Hrvoje Niksic <hniksic(a)srce.hr&gt; writes: Personally I think that is generally the wrong way to do this. A more loose coupling between redisplay engine and the lisp code should be preferred (i.e. a lazy-shot style asynchronous feedback mechanism. Writing a better C implementation of that and generalising it into an on-demand.el is still on my long term TODO list. It is however after "write thesis"). For instance what do you if multiple windows have this buffer visible? This indeed seems wrong. I think the non-GUARANTEE values is wrong. It doesn't seem to be more expense to compute the correct value. However it might be that there is code that depends on the behaviour there is now. Because I think the window-start value is always GUARANTEEd. Jan